Valve/sensor assemblies

ABSTRACT

In a first aspect, a valve/sensor assembly is provided that includes a door assembly. The door assembly has (1) a first position adapted to seal an opening of a chamber; (2) a second position adapted to allow at least a blade of a substrate handler to extend through the opening of the chamber; and (3) a mounting mechanism adapted to couple the door assembly to the chamber. The valve/sensor assembly also includes a sensor system having a transmitter and a receiver adapted to detect a presence of a substrate and to communicate through at least a portion of the door assembly. Systems, methods and computer program products are provided in accordance with this and other aspects.

[0001] The present application is a division of U.S. patent applicationSer. No. 09/895,437 filed Jun. 30, 2001, which claims priority from U.S.Provisional Patent Application Serial No. 60/216,981, filed Jul. 7,2000. Both of these patent applications are incorporated by referenceherein in their entirety.

FIELD OF THE INVENTION

[0002] The present invention relates to detection technology, and morespecifically to detection technology that is used to detect asemiconductor wafer.

BACKGROUND OF THE INVENTION

[0003] Semiconductor wafers are processed within automated fabricationtools comprising a plurality of chambers. FIG. 1A is a schematic topplan view, in pertinent part, of an automated semiconductor devicefabrication tool 11. The exemplary fabrication tool 11 of FIG. 1Acomprises a first transfer chamber 13 and a second transfer chamber 15.A first and a second wafer handler 17, 19, each having a blade (notshown) that may support a wafer, are housed in the first transferchamber 13 and the second transfer chamber 15, respectively. The firsttransfer chamber 13 and the second transfer chamber 15 are bothmonolithic and have various chambers coupled thereto.

[0004] A pair of loadlocks 21, 23 and a pair of pass-through chambers25, 27 are coupled to the first transfer chamber 13. Other chambers suchas degassing or oxide-etch chambers (shown in phantom) also may becoupled to the first transfer chamber 13. The pass-through chambers 25,27 and a plurality of processing chambers 29, 31, 33, and 35, which areconfigured to perform various semiconductor device fabrication processes(e.g., chemical vapor deposition, sputter deposition, etc.), are coupledto the second transfer chamber 15. A controller 36 controls wafertransfer and processing within the fabrication tool 11.

[0005] Typically the environment of each chamber must be selectivelyisolated from the environments of neighboring chambers to prevent crosscontamination, and to enable the various chambers to be maintained atpressures that differ according to the process to be performed therein.To achieve such selective isolation, each chamber is provided with aslit (not shown) through which one of the wafer handlers 17, 19 mayextend to transport wafers to and from the chamber. The slit of eachchamber is selectively sealed with a door assembly 37 (typicallyreferred to as a slit valve for vacuum applications, and as a gate valvefor non-vacuum applications).

[0006] As the wafer handlers 17, 19 transport a wafer through slits andthrough various chambers, the wafer must be accurately positioned on theblade of each wafer handler 17, 19 to avoid breaking or damaging thewafer (by the wafer falling or striking a chamber component), to ensureproper placement of the wafer on a wafer pedestal so as to preventdeposition of material on the wafer pedestal during processing and toensure complete coverage during deposition of a material layer on thewafer, etc. Accordingly, to ensure accurate wafer positioning (so as toavoid wafer damage/breakage or deposition on a wafer pedestal, so as toensure complete material layer coverage on a wafer, etc.), numerouswafer detection devices (e.g., sensor systems) exist in fabricationtools to determine a wafer's position. Such sensor systems are typicallylocated in the transfer chambers 13, 15, although sensor systems may belocated in other chambers as well. A fabrication tool may employmultiple sensor systems.

[0007] Two main types of sensor systems are conventionally used withinfabrication tools. Both systems employ sensors to detect a wafer'sposition as the wafer enters and/or leaves a chamber. In the firstsystem, a sensor is mounted to the outside of a processing chamber andmonitors wafer position via a quartz window formed in the processingchamber. That is, a wafer is observed through the quartz window as thewafer enters and exits the processing chamber. In the second system, asensor is mounted within a transfer chamber and monitors a wafer'sposition as the wafer enters and exits the transfer chamber. The twoconventional sensor systems may be used individually or jointly in thefabrication tool 11.

[0008] Both types of sensor systems have disadvantages. With regard tothe first sensor system, material may deposit on the quartz windowduring processing and affect sensor resolution/accuracy. With regard tothe second system, sensor mounting locations typically must be machinedwithin the transfer chamber (e.g., a potentially difficult and timeconsuming process).

[0009]FIG. 1B is a partially exploded perspective view of the transferchamber 15 of FIG. 1A that is useful in explaining another conventionalsensor system. The transfer chamber 13 of FIG. 1A may be similarlyconfigured.

[0010] As stated, in one conventional sensor system, a sensor may bemounted within a transfer chamber and monitor a wafer's position as thewafer enters and exits the transfer chamber. For example, in FIG. 1B, aplurality of light transmitters 39 a-b (shown in phantom) are mounted toa lid 41 of the transfer chamber 15 (e.g., to one or more quartz windowsor viewports not shown) and generate light beams 44 a-b (shown inphantom) that are directed toward a bottom 43 of the transfer chamber15. A plurality of receivers 45 a-b (e.g., photodetectors) are mountedto the bottom 43 of the transfer chamber 15 (e.g., the bottom 43 ismachined to accept the receivers 45 a-b), and are positioned to receivethe light beams 44 a-b generated by the transmitters 39 a-b.

[0011] By monitoring when the light beams 44 a-b are broken by a wafer Wpositioned on a blade B (shown in phantom) of the wafer handler 19(e.g., as the wafer W is positioned for entry through a slit 47 of thetransfer chamber 15 and/or as the wafer W travels through the slit 47 ofthe transfer chamber 15), the position of the wafer W on the blade B maybe determined by conventional techniques.

[0012] A reflection based system wherein light beams 44 a-b arereflected off of the wafer W toward the receivers 45 a-b also may beemployed to determine wafer position (e.g., if both the transmitters 39a-b and the receivers 45 a-b are mounted to either the lid 41 or thebottom 43). In either case, machining of one or more of the lid 41 andthe bottom 43 may be required.

[0013] In one conventional system termed an on-the-fly (OTF) centerfinder, the transmitters 39 a-b and the receivers 45 a-b are employed tosense the wafer W as the wafer handler 19 rotates, and to determinewafer center information based thereon. Typically three lighttransmitters and three receivers are employed. The three lighttransmitters conventionally are mounted to the bottom 43 of the transferchamber 15, outside the transfer chamber 15. Holes are machined in thebottom 43 to allow the light beams from the transmitters to travel intothe transfer chamber 15. The three receivers typically are mounted tothe lid 41, outside the transfer chamber 15. Holes are machined in thelid 41 to allow the light beams from the transmitters to travel to thereceivers.

[0014] In operation, the OTF center finder monitors (via the receiversmounted to the lid 41 of the transfer chamber 15) when light beamsemitted by the transmitters mounted to the bottom 43 of the transferchamber 15 are blocked by the wafer W (e.g., as during such timeperiods, no light beams are detected by the receivers mounted to the lid41). A corresponding “blocked” light beam signal is sent to a controller(not shown), and the controller determines a step count of a motor (notshown) that rotates the wafer handler 19. The controller then employs analgorithm to determine the center of the wafer W in relation to thecenter of the wafer handler 19. The wafer W thereby may be placed in anexact location as it travels through the slit 47.

[0015] As well as requiring machining of holes in the transfer chamber15, the OTF center finder suffers from other drawbacks. For example, thewafer W may move on the blade B during rotation (after passing the lightbeams 44 a-b). Wafer position determinations thereby may be inaccurate.

[0016] Accordingly, an improved method and apparatus is needed fordetecting wafer position during wafer transfer.

SUMMARY OF THE INVENTION

[0017] In accordance with a first aspect of the invention, avalve/sensor assembly is provided that includes a door assembly. Thedoor assembly has (1) a first position adapted to seal an opening of achamber; (2) a second position adapted to allow at least a blade of asubstrate handler to extend through the opening of the chamber; and (3)a mounting mechanism adapted to couple the door assembly to the chamber.The valve/sensor assembly also includes a sensor system having atransmitter and a receiver adapted to detect a presence of a substrateand to communicate through at least a portion of the door assembly.

[0018] In a second aspect of the invention, a valve/sensor assembly isprovided that includes a door assembly having (1) a first positionadapted to seal an opening of a chamber; (2) a second position adaptedto allow at least a blade of a substrate handler to extend through theopening of the chamber; and (3) a mounting mechanism adapted to couplethe door assembly to the chamber, the mounting mechanism having aviewport. The valve/sensor assembly also includes a sensor system havinga transmitter and a receiver adapted to detect a presence of a substrateand to communicate through the viewport of the mounting mechanism.

[0019] Systems, methods and computer program products are provided inaccordance with these and other aspects of the invention. Each computerprogram product may comprise a medium readable by a computer (e.g., acarrier wave signal, a floppy disk, a compact disk, a hard drive, etc.).

[0020] Other features and aspects of the present invention will becomemore fully apparent from the following detailed description, theappended claims and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1A is a schematic top plan view, in pertinent part, of aconventional automated semiconductor device fabrication tool;

[0022]FIG. 1B is a partially exploded perspective view of the transferchamber of FIG. 1A that is useful in explaining conventional sensorsystems; FIG. 2 is a partial sectional view of the fabrication tool ofFIG. 1A taken along the line 2-2 of FIG. 1A, which shows an angled doorassembly;

[0023] FIGS. 3A-B are side views of the angled door assembly of FIG. 2in an opened and closed position, respectively;

[0024]FIG. 4 is a perspective view of a first inventive valve/sensorassembly that employs an angled door assembly that is similar to theangled door assembly of FIGS. 2-3B;

[0025]FIG. 5 is a schematic side elevational view of a conventionalvertical door assembly;

[0026]FIG. 6 is a side perspective view of a second inventivevalve/sensor assembly;

[0027]FIG. 7 is a top view of the second inventive valve/sensor assemblyof FIG. 6;

[0028]FIG. 8 is a bottom perspective view of the second inventivevalve/sensor assembly of FIG. 6;

[0029]FIG. 9 is a perspective view of the second inventive valve/sensorassembly of FIG. 6 shown coupled to the transfer chamber of FIG. 1A;

[0030]FIG. 10 is an exploded isometric view of an alternative,conventional vertical door assembly that may be used in place of thevertical door assembly of FIG. 5 within the inventive valve/sensorassembly of FIGS. 6-9;

[0031]FIG. 11 is a schematic view of a conventional arm employable bythe wafer handler of FIGS. 1A and 1B;

[0032]FIG. 12 is a side view of an exemplary through-beam sensor systemthat may determine a wafer's position on the blade of FIG. 11 of thewafer handler of FIG. 1A;

[0033]FIG. 13 is a flowchart of an exemplary process for determining awafer's position on a wafer handler using the through-beam sensor systemof FIG. 12; and

[0034]FIG. 14 is a partial side view of an exemplary reflection-basedsensor system that may determine a wafer's position on the blade of FIG.11 of the wafer handler of FIG. 1A.

DETAILED DESCRIPTION

[0035] In accordance with the present invention, a novel sensor systemis provided wherein sensors (e.g., transmitters and/or receivers)employed during conventional wafer position and/or center determinationsare attached to and/or may communicate through a door assembly (e.g., aslit valve bracket) employed to seal an opening of a transfer chamber(e.g., the slit 47 of FIG. 1B). In this manner, additional holes orsensor mounting locations need not be machined within the transferchamber (e.g., within the bottom 43 of the transfer chamber 15 of FIG.1B). Sensors may be positioned such that a light beam is broken by awafer just before the wafer exits the transfer chamber (e.g., as thewafer enters the slit 47 and travels to a processing chamber such as oneof the processing chambers 29-35 of FIG. 1A). In this manner, ascompared to an OTF center finder, a wafer is significantly less likelyto move (e.g., relative to a wafer handler blade that supports thewafer) after the wafer passes the sensors or exits the transfer chamber.Additionally, controller software employed during wafer positioningcalculations is simplified because sensors may be positioned so thatonly wafers exiting the transfer chamber may break the light beams ofthe sensors (e.g., other wafers being transported between processingchambers, or portions of a wafer handler cannot inadvertently break thelight beam of a sensor). Only one sensor bank per transfer chamberopening is required.

[0036] As stated, the inventive sensor system employs sensors attachedto a door assembly that seals an opening of a transfer chamber. Ingeneral, any type of door assembly may be so configured (e.g., gatevalve assemblies, slit valve assemblies, etc.). Several exemplary doorassemblies configured in accordance with the present invention aredescribed below. It will be understood that other door assemblies may besimilarly configured.

[0037] CONVENTIONAL ANGLED DOOR ASSEMBLY

[0038]FIG. 2 is a partial sectional view of the fabrication tool 11 ofFIG. 1A taken along the line 2-2 of FIG. 1A, which shows an angled doorassembly 37 a. The angled door assembly 37 a includes a sealing surface38 a that typically moves up and down at a 45 degree angle (shown byangle X in FIG. 2) relative to a bottom wall 139 of the transfer chamber15 so as to selectively engage and seal a sealable opening 143 a (e.g.,a slit) of the transfer chamber 15 as shown in FIG. 2.

[0039] FIGS. 3A-B are side views of the angled door assembly 37 a ofFIG. 2 in an opened and closed position, respectively, and illustratethe angled door assembly 37 a in more detail than that shown in FIG. 2.The sealing surface 38 a of the angled door assembly 37 a moves betweenthe opened position (FIG. 3A) wherein the angled door assembly 37 a doesnot seal the opening 143 a and the closed position (FIG. 3B) wherein theangled door assembly 37 a seals the opening 143 a.

[0040] As shown in FIGS. 3A-B, the opening 143 a is surrounded by avalve seat 165, whereby the sealing surface 38 a of the angled doorassembly 37 a selectively engages the valve seat 165 to close theopening 143 a. The sealing surface 38 a of the angled door assembly 37 amay have a groove (not shown) formed therein to contain an O-ring 172.The sealing surface 38 a is positioned to contact the valve seat 165when the angled door assembly 37 a is in a closed position (FIG. 3B).

[0041] The angled door assembly 37 a also may comprise an elongatedshaft portion 173 (of an actuator assembly 175) that allows the angleddoor assembly 37 a to move between the opened position (FIG. 3A) and theclosed position (FIG. 3B). The actuator assembly 175 may comprise acylinder 177 that has a piston 179 that drives the shaft port 173 (andthe sealing surface 38 a coupled thereto) between the opened and closedpositions. The angled door assembly 37 a may be configured, for example,as described in U.S. Pat. No. 5,363,872, issued Nov. 15, 1994, theentire disclosure of which is incorporated herein by this reference.

[0042] In operation, the wafer handler 19 (FIG. 1A or FIG. 1B) transfersthe wafer W toward the sealable opening 143 a (e.g., slit 47 in FIG.1B). As the wafer handler 19 approaches the sealable opening 143 a, thesealing surface 38 a of the angled door assembly 37 a, upon actuation,moves to the opened position (FIG. 3A) so as to allow the blade of thewafer handler 19 to extend through the opening 143 a. The wafer W thenmay be transferred to another chamber via the blade of the wafer handler19.

[0043] FIRST INVENTIVE VALVE/SENSOR ASSEMBLY

[0044]FIG. 4 is a perspective view of a first inventive valve/sensorassembly 445 that employs an angled door assembly 437 that is similar tothe angled door assembly 37 a of FIGS. 2-3B. The inventive valve/sensorassembly 445 may detect the position of a wafer within a chamber such asone of the transfer chambers 13, 15 of FIG. 1A.

[0045] With reference to FIG. 4, the inventive valve/sensor assembly 445includes a mounting mechanism 447 for mounting the angled door assembly437 to a bottom of a transfer chamber (e.g., to the bottom 43 of thetransfer chamber 15 of FIG. 1B), a sensor system 448 and a controller449 coupled to the sensor system 448. The angled door assembly 437 maybe positioned so as to seal one of the various slits of the transferchamber 15, such as slit 47 in FIG. 1B as described previously withreference to the door assembly 37 a of FIGS. 2-3B.

[0046] The sensor system 448 may detect the position of a wafer and mayoutput a signal indicative of the position of the wafer by using one ormore conventional techniques. The controller 449 may receive the signaloutput by the sensor system 448. In the exemplary embodiment of FIG. 4,the sensor system 448 includes a light transmitter 451, such as one ormore light emitting diodes (LEDs), and a receiver 453, such as one ormore photodetectors.

[0047] In one embodiment, the mounting mechanism 447 is configured tocouple to the bottom wall 43 (shown in phantom in FIG. 4) of thetransfer chamber 15, via bolts or some other fastener (not shown). Themounting mechanism 447 may comprise a bracket that includes a horizontalmounting platform 457 adapted to couple to the bottom wall 43 of thetransfer chamber 15, and two vertical sidewalls 459 a, 459 b coupled tothe horizontal mounting platform 457. The mounting platform 457 and thesidewalls 459 a, 459 b may be machined from a single piece of material(if desired). Any other configuration may be similarly employed.

[0048] The horizontal mounting platform 457 comprises an opening (notshown) in which the angled door assembly 437 is mounted, and a viewport463. In one or more embodiments of the invention, the viewport 463allows the light transmitter 451 and the receiver 453 to communicate asdescribed below. The viewport 463 may comprise, for example, a quartzwindow that allows a light beam to travel therethrough, and the lighttransmitter 451 and/or the receiver 453 to be isolated from theenvironment of the transfer chamber 15.

[0049] In the embodiment of FIG. 4, the light transmitter 451 is coupledto the lid 41 of the transfer chamber 15 (e.g., is mounted to the lid 41outside the transfer chamber 15), and generates a plurality of lightbeams 465 a-b which travel through the lid 41 (e.g., through a pluralityof holes 467 a-b in the lid 41, or one or more quartz windows orviewports (not shown) of the lid 41) into the transfer chamber 15 towardthe viewport 463. When not obstructed by the wafer W, the light beamstravel through the viewport 463 and are detected by the receiver 453.

[0050] The receiver 453, for example, may be coupled to the mountingmechanism 447 or otherwise disposed below the viewport 463.Alternatively, the transmitter 451 may be disposed below the viewport463, and the receiver 453 may be coupled to the lid 41. If areflection-based system is employed, both the transmitter 451 and thereceiver 453 may be coupled to the mounting mechanism 447 (or otherwisedisposed below the viewport 463). In either case, because thetransmitter 451 and the receiver 453 communicate through the inventivevalve/sensor assembly 445, additional mounting locations and/or holesneed not be machined within the bottom 43 of the transfer chamber 15 toallow the transmitter 451 and the receiver 453 to communicate. Note thatmore or fewer than two transmitters and receivers may be employed.

[0051] In operation, as the wafer W leaves the transfer chamber 15 (oras the wafer W re-enters the transfer chamber 15) from any of thevarious chambers coupled thereto, the wafer W breaks one or both of thelight beams 467 a-b. In response thereto, a signal (e.g., from thereceiver 453) is communicated to the controller 449. The controller 449then may compute the position of the wafer W on the wafer handler 19using any conventional technique. For example, a position value may becomputed for the wafer W and compared to a position value previouslystored for a wafer properly positioned on the wafer handler 19. Basedthereon, a wafer offset value may be calculated. If the wafer W ismisaligned (e.g., if the position of the wafer W is off-center relativeto a blade of the wafer handler 19), the wafer handler 19 may thencenter the wafer W relative to an opening (e.g., slit 47 in FIG. 1B)through which the wafer W is to travel or relative to a wafer support onwhich the wafer W is to be placed (e.g., using any conventionalwafer-positioning technique).

[0052] As previously stated, any conventional door assembly may beconfigured with a sensor system in accordance with the presentinvention. Accordingly, exemplary, additional embodiments of the presentinvention are described further below.

[0053] FIRST CONVENTIONAL VERTICAL DOOR ASSEMBLY

[0054]FIG. 5 is a schematic side elevational view of a conventionalvertical door assembly 37 b. The vertical door assembly 37 b includes asealing surface 38 b that moves up and down parallel to a surface 544(e.g., a surface of the transfer chamber 15 of FIG. 1A or of aprocessing chamber) having a sealable opening 543 b (e.g., slit 47 inFIG. 1B), rather than moving at a 45 degree angle as with the angleddoor assembly 37 a of FIG. 2.

[0055] The vertical door assembly 37 b may comprise a paddle-shapedstructure 545, having the sealing surface 38 b coupled to an elongatedshaft portion 547 that extends downward from the sealing surface 38 b.The vertical door assembly 37 b also may comprise a first air cylinder549 a, coupled to a lower portion 551 of the paddle-shaped structure545, that allows movement of the sealing surface 38 b between a loweredposition (not shown) wherein the vertical door assembly 37 b does notocclude the opening 543 b and an elevated position (FIG. 5) wherein thesealing surface 38 b occludes the opening 543 b. When the sealingsurface 38 b is in the elevated position (FIG. 5), upon actuation, asecond air cylinder 549 b pushes against the lower portion 551 so as topivot the sealing surface 38 b toward and into contact with the sealableopening 543 b. The sealing surface 38 b thereby seals the sealableopening 543 b.

[0056] SECOND INVENTIVE VALVE/SENSOR ASSEMBLY

[0057] FIGS. 6-9 show various views of a second inventive valve/sensorassembly 645 that employs the vertical door assembly 37 b of FIG. 5.Specifically, FIG. 6 is a side perspective view of the second inventivevalve/sensor assembly 645; FIG. 7 is a top view of the second inventivevalve/sensor assembly 645; FIG. 8 is a bottom perspective view of thesecond inventive valve/sensor assembly 645; and FIG. 9 is a perspectiveview of the second inventive valve/sensor assembly 645 shown coupled tothe transfer chamber 15.

[0058] The inventive valve/sensor assembly 645 may comprise a mountingmechanism 647, a sensor system 688 (represented by a transmitter 688 aand a receiver 688 b shown in phantom), and a controller 649 coupled tothe sensor system 688. As with the sensor system 448 of the firstinventive valve/sensor assembly 445, the sensor system 688 may detectthe position of a wafer by using one or more of the previously describedtechniques, or one or more of the techniques described below with FIGS.12-14. The controller 649 may receive a signal output by the sensorsystem 688 (e.g., a signal from the receiver 688 b of the sensor system688 that indicates when a light beam transmitted from the transmitter688 a to the receiver 688 b has been blocked). The inventivevalve/sensor assembly 645 may include multiple sensor systems 688, thetransmitter 688 a may include multiple light sources and/or the receiver688 b may include multiple light detectors. The locations of thetransmitter 688 a and the receiver 688 b are merely exemplary.

[0059] In one embodiment, the mounting mechanism 647 may comprise ahousing (e.g., a structure that may be inserted between a transferchamber and another chamber, and that contains a conventional doorassembly adapted to engage and seal a sealable opening such as the doorassembly 37 b of FIG. 5) that is coupled to a sidewall 682 (FIG. 9) ofthe transfer chamber 15, via bolts or some other fastener (not shown).The housing may comprise an adapter block 683 having an opening that mayaccommodate different wafer sizes and that may accommodate differentsealing plate sizes.

[0060] In the embodiments of FIGS. 6-9, the adapter block 683 comprisesa rectangular-shaped structure that has six sides. A bottom wall 685(FIG. 8) has a region (not shown) that allows the vertical door assembly37 b of FIG. 5 to move up and down so as to selectively seal an openingof the transfer chamber 15, such as the slit 47 of FIG. 1B. A top wall689 (FIG. 7) and the bottom wall 685 (FIG. 8) may have a top slot 693(FIG. 7) and a bottom slot 695 (FIG. 8), respectively, such that thetransmitter 688 a and/or the receiver 688 b may be inserted therein. Forexample, the light transmitter 688 a may be inserted in the top slot 693(FIG. 7), and the receiver 688 b may be inserted in the bottom slot 695(FIG. 8). For embodiments that employ reflection-based sensor systems(as described below with reference to FIG. 14), the top slot 693 or thebottom slot 695 may contain both the transmitter 688 a and the receiver688 b. Both slots 693, 695 may contain a quartz window, such that eachrespective sensor may be isolated from processing tool environments.

[0061] The top wall 689 may comprise a viewport 663 b (FIG. 7) and/ormay comprise a removable lid 697 (FIG. 7), coupled to the remainder ofthe inventive valve/sensor assembly 645, via a latching mechanism 698(FIG. 7). The viewport 663 b (e.g., a quartz window) may provideunobstructed view of a wafer as the wafer passes through the inventivevalve/sensor assembly 645. The removable lid 697 provides access intothe adapter block 683 so as to allow repair of the vertical doorassembly 37 b or so as to allow cleaning of the adapter block 683 and/orthe sensor system 688. A front wall 699 (FIG. 6) and a back wall 700(FIG. 8) each have an aperture 703 (FIG. 6), 705 (FIG. 8) aligned so asto allow the wafer handler 19 and a wafer positioned thereon to passthrough the adapter block 683 as the wafer handler 19 transports thewafer between the transfer chamber 15 and another chamber coupledthereto.

[0062] In operation, the wafer handler 19 transfers a wafer toward thesealable opening 543 b (FIG. 5). As the wafer handler 19 approaches thesealable opening 543 b, the vertical door assembly 37 b, upon actuation,moves to a lowered position so as to allow a blade of the wafer handler19 to extend through the opening 543 b and through the adapter block683. A wafer thereby may be transferred through the inventivevalve/sensor assembly 645 and into another chamber.

[0063] Unlike the inventive valve/sensor assembly 445 of FIG. 4, whichdetects the position of a wafer while it is still within the transferchamber 15, the inventive valve/sensor assembly 645 of FIGS. 6-9 detectsthe position of a wafer as the wafer passes through the adapter block683 (e.g., using one or more of the previously described techniques, orone or more of the techniques described below with reference to FIGS.12-14).

[0064] Because the exact locations of the light transmitter 688 a andthe receiver 688 b are known relative to each other, the number ofvariables of the sensor system 688 is reduced, which may simplify thecalibration requirements. Further, the modularity of the adapter block683 allows the inventive valve/sensor assembly 645 to be easily replacedor repaired.

[0065] Although the inventive valve/sensor assembly 645 has beendescribed with reference to the vertical door assembly 37 b of FIG. 5,it will be understood that other door assemblies may be used in place ofthe vertical door assembly 37 b, such as the vertical door assembly ofFIG. 10 (described below).

[0066] SECOND CONVENTIONAL VERTICAL DOOR ASSEMBLY

[0067]FIG. 10 is an exploded isometric view of an alternative,conventional vertical door assembly 37 c that may be used in place ofthe vertical door assembly 37 b of FIG. 5 within the inventivevalve/sensor assembly 645 of FIGS. 6-9. As stated, any otherconventional vertical door assembly may be similarly employed.

[0068] With reference to FIG. 10, the vertical door assembly 37 cemploys at least one inflatable member 1111 adapted to selectively movea frontplate 1113 of the vertical door assembly 37 c toward a sealableopening (not shown), such as the sealable opening 543 b of FIG. 5. Thevertical door assembly 37 c also may include a backplate 1115 coupled tothe frontplate 1113. The inflatable member 1111 is disposed between thefrontplate 1113 and the backplate 1115 and is adapted to move thefrontplate 1113 into sealing engagement with an opening of a chamber(e.g., the slit 47 of FIG. 1B) when inflated. The vertical door assembly37 c may be configured as described in U.S. patent application Ser. No.09/238,251, filed Jan. 27, 1999 (AMAT No. 2826/ATD/MBE) the entiredisclosure of which is incorporated herein by this reference. Theinventive valve/sensor assembly 645 operates similarly whether the doorassembly 37 b (FIG. 5) or the door assembly 37 c (FIG. 10) is employed.

[0069] CONVENTIONAL ARM OF WAFER HANDLER

[0070]FIG. 11 is a schematic view of a conventional arm 1117 employableby the wafer handler 19 of FIGS. 1A and 1B. The arm 1117 may be employedduring wafer positioning and/or centering in accordance with the presentinvention. Any other conventional wafer handler arm may be similarlyemployed.

[0071] With reference to FIG. 11, the arm 1117 may comprise a wrist1119, a blade 1121 mounted to the wrist 1119, a pair of grippers 1123positioned at the proximal end of the blade 1121, and a pair ofprojections or “shoes” 1125 positioned at the distal end of the blade1121. The shoes 1125 and the grippers 1123 are positioned to form apocket 1127 such that a wafer W (shown in phantom) may be inserted intothe pocket 1127. The blade 1121 comprises a center hole 1129, which maybe used to determine the presence of the wafer W on the blade 1121 asdescribed below, and a slot 1131 positioned adjacent the grippers 1123,which may be used to determine the position of the wafer on the blade1121 also as described below.

[0072] Upon actuation of a stepper motor (not shown), the grippers 1123,which are described in detail in U.S. Pat. No. 5,980,194, issued Nov. 9,1999, the entire disclosure of which is incorporated herein by thisreference, may retract away from the projections 1125 to enlarge thepocket 1127 as the wafer W is inserted onto the blade 1121. The grippers1123 then may extend toward the projections 1125 to close the pocket1127 after the wafer W is placed onto the blade 1121, thereby clampingthe wafer W in the pocket 1127.

[0073] During operation of the wafer handler 19 (when the arm 1117 isemployed) with the inventive valve/sensor assembly 445 of FIG. 4 (or theinventive valve/sensor assembly 645 of FIG. 6), the controller 449 (orthe controller 649) may count the number of steps (e.g., of a steppermotor (not shown) that drives the wafer handler 19) that the waferhandler 19 has moved between one reference point (e.g., a point wherethe edge of the wafer W blocks a light beam from transmitter 451 or 688a from reaching receiver 453 or 688 b) and another reference point(e.g., a point where the slot 1131 allows the light beam to passtherethrough and to the receiver 453 or 688 b). The controller 449 (orthe controller 649) then may derive an offset for proper positioning ofthe wafer W.

[0074] Positioning techniques may function by using the followinggeneral process. First, the sensor system 448, 688 is calibrated bycollecting data from a wafer that is properly positioned on the blade1121. Then, to determine the position of a wafer being processed in thetool 11 (FIG. 1A), positional points are collected when an edge of theslot 1131 crosses a light beam (from transmitter 451 or 688 a) and whenan edge of the wafer crosses the light beam. The positional points arecompared to the calibration data to calculate a wafer offset value. Fromthe wafer offset value, the wafer handler 19 may center the wafer on asubstrate support (not shown) of another chamber (e.g., one of theprocessing chambers 29-35 of FIG. 1A) by adjusting the position of theblade 1121 relative to the substrate support (such that the wafer iscentered above the wafer support).

[0075] EXEMPLARY THROUGH-BEAM SENSOR SYSTEM

[0076]FIG. 12 is a side view of an exemplary through-beam sensor system1201 that may determine a wafer's position on the blade 1121 (FIG. 11)of the wafer handler 19 (FIG. 1A). A similar through-beam sensor systemmay be employed with the inventive valve/sensor assemblies 445, 645.With reference to FIG. 12, the through-beam sensor system 1201 comprisesa transmitter 1203 positioned so as to transmit a light beam 1205 to areceiver 1207 “through” a path traveled by the wafer handler 19 as thewafer handler 19 transports a wafer W. The transmitter 1203 may bepositioned, for example, on the lid 41 of the transfer chamber 15, andthe receiver 1207 may be coupled to the mounting plate 457 of theinventive valve/sensor assembly 445. Other locations may be similarlyemployed. As described further below, when the wafer W is positionedbetween the transmitter 1203 and the receiver 1207, the wafer W blocksthe light beam 1205 emitted by the transmitter 1203, and the receiver1207 does not detect the light beam 1205. When the wafer W is notpositioned between the transmitter 1203 and the receiver 1207, thereceiver 1207 detects the light beam 1205.

[0077] EXEMPLARY PROCESS FOR THROUGH-BEAM SENSOR SYSTEM

[0078]FIG. 13 is a flowchart of an exemplary process 1300 fordetermining a wafer's position on the wafer handler 19 using thethrough-beam sensor system 1201 of FIG. 12. Other processes may besimilarly performed.

[0079] Referring to FIG. 13, in step 1301, the sensor system 1201 iscalibrated by collecting data from a wafer that is properly centered onthe blade 1121 of the wafer handler 19 as the wafer travels between thetransmitter 1203 and the receiver 1207. The data may include, forexample, (1) a measured distance between a trailing edge of the properlycentered wafer and a trailing edge of the slot 1131; (2) the size of thewafer (e.g., 5, 6, or 8 inch); (3) a measured distance between two ormore reference points, as the wafer handler 19 transports the properlycentered wafer; (4) a measured distance between the leading and thetrailing edges of the slot 1131; (5) the location of the transmitter1203 and the receiver 1207; and (6) the speed at which the blade 1121 ofthe wafer handler 19 travels. The data is stored and is used todetermine a wafer offset value of a wafer W (e.g., a subsequent, notnecessarily properly centered wafer) that is transported by the waferhandler 19 as described below. The data may be stored, for example, in acontroller 1249 (FIG. 12), the controller 449 (FIG. 4), the controller649 (FIG. 6) or the like.

[0080] In step 1303, the wafer handler 19 transports the wafer W fromthe transfer chamber 15 to one of the various chambers coupled to thetransfer chamber 15 (e.g., one of the processing chambers 29-35). As thewafer handler 19 transports the wafer W from the transfer chamber 15 toanother chamber, the leading edge of the wafer W (the distal edge of thewafer W on the blade 1121) blocks the light beam 1205 from thetransmitter 1203 so that the receiver 1207 does not detect the lightbeam 1205. After the wafer W passes the light beam 1205, the slot 1131allows the light beam 1205 to pass through the wafer handler 19 so as tocontact the receiver 1207.

[0081] In step 1305, the change in the amount of light detected by thereceiver 1207 between when the wafer W interrupts the light beam 1205and when the slot 1131 allows the light beam 1205 to pass through thewafer handler 19 is determined. Note that an output of the receiver 1207may have a first signal value when the light beam 1205 contacts thereceiver 1207 (e.g., a non-interrupted state such as when the light beam1205 passes through the slot 1131), and may have a second signal valuewhen the light beam 1205 does not contact the receiver 1207 (e.g., aninterrupted state such as when the light beam 1205 strikes the wafer W).

[0082] The output signal of the receiver 1207 thus changes from thefirst signal value to the second signal value when the light beam 1205(which strikes the receiver 1207 before the wafer handler 19 crosses thepath of the light beam) becomes blocked by the leading edge of the waferW. After the trailing edge of the wafer W passes the light beam 1205,the output signal of the receiver 1207 changes from the second signalvalue to the first signal value when the light beam 1205 passes throughthe slot 1131. After the trailing edge of the slot 1131 passes the lightbeam 1205, the output signal of the receiver 1207 changes from the firstsignal value back to the second signal value.

[0083] In step 1307, the controller 1249 counts the number of steps thatthe blade 1121 of the wafer handler 19 has moved between when the outputsignal of the receiver 1207 changes from the second signal value(interrupted state) to the first signal value (non-interrupted state)and back to the second signal value (interrupted state) (e.g., the timeperiod during which the receiver 1207 outputs the first signal value).The controller 1249 converts the step count into a position value instep 1309 (e.g., by means of lookup table that stores the calibratedvalues previously described). Then, in step 1311, the position value iscompared to the calibrated data to calculate a wafer offset value.Specifically, an exact match between the position value for the wafer Wand the position value previously stored for the properly centered wafer(step 1301) represents a centered wafer. If the position value for thewafer W differs from the position value previously stored for theproperly centered wafer, then the wafer W is not properly centered.

[0084] In step 1312, the wafer offset value is compared to apredetermined value. If the wafer offset value is greater than thepredetermined value, in step 1313, the controller 1249 may stop thewafer handler 19 so that an operator may manually center the wafer W onthe blade 1121 (and the process 1300 may end); otherwise, in step 1315,if the wafer offset value does not exceed the predetermined value, thenwafer transfer continues as described below.

[0085] Following step 1315, in step 1317, the controller 1249 calculatescorrection values for the wafer handler 19 from the wafer offset value.Based on the correction values, the controller 1249 alters the linearand/or rotational translations of the wafer handler 19 so as to adjustfor wafer misalignment and to center the wafer W (step 1319). The waferW also may be centered using the technique described in U.S. Pat. No.5,563,798, issued October, 1996, the entire disclosure of which isincorporated herein by this reference. Assuming the wafer handler 19transports the wafer W from the transfer chamber 15 to the processingchamber 29, the wafer W may be placed on (e.g., centered on) a substratesupport (not shown) of the processing chamber 29 and processed.

[0086] In step 1321, the wafer handler 19 transports the wafer W from achamber coupled to the transfer chamber 15 (e.g., one of the processingchambers 29-35 of FIG. 1A) to the transfer chamber 15. As the waferhandler 19 transports the wafer W to the transfer chamber 15, the slot1131 allows the light beam 1205 to pass through the wafer handler 19 soas to contact the receiver 1207. After the slot 1131 passes the lightbeam 1205, the leading edge of the wafer W blocks the light beam 1205.

[0087] In step 1323, the change in the output signal of the receiver1207 between when the slot 1131 allows the light beam 1205 to passthrough the wafer handler 19 and when the leading edge of the wafer Winterrupts the light beam 1205 is determined. When the slot 1131 allowsthe light beam 1205 to pass, the output signal of the receiver 1207 isthe first signal value. When the leading edge of the wafer W interruptsthe light beam 1205, the output signal of the receiver 1207 is thesecond signal value.

[0088] The output signal of the receiver 1207 changes from the firstsignal value to the second signal value when the light beam 1205traveling through the slot 1131 becomes blocked by the leading edge ofthe wafer W. In step 1325, the controller 1249 counts the number ofsteps that the wafer handler 19 has moved while the light beam 1205passes through the slot 1131 (e.g., the time period during which thereceiver 1207 outputs the first signal value). The controller 1249converts the step count into a position value in step 1327. Then, instep 1329, the position value is compared to the calibrated data tocalculate the wafer offset value. Thereafter, in step 1331, the wafer Wis centered as described above with reference to steps 1312-1319. Theprocess 1300 then ends.

[0089] As stated previously, the inventive valve/sensor assembly 445 ofFIG. 4, the inventive valve/sensor assembly 645 of FIG. 6 or any othervalve/sensor assembly configured in accordance with the presentinvention may employ the process 1300 or a variation thereof. Thecontroller 449, 649 and/or 1249 may comprise computer program code forperforming one or more of the steps of the process 1300 and may includeone or more computer program products.

[0090] EXEMPLARY REFLECTION-BASED SENSOR SYSTEM

[0091]FIG. 14 is a partial side view of an exemplary reflection-basedsensor system 1401 that may determine a wafer's position on the blade1121 (FIG. 11) of the wafer handler 19 (FIG. 1A). A similarreflection-based sensor system may be employed with the inventivevalve/sensor assemblies 445, 645 or any other valve/sensor assemblyconfigured in accordance with the present invention.

[0092] With reference to FIG. 14, the refection-based sensor system 1401comprises a transmitter 1403 and a receiver 1405, which may or may notbe contained within a single housing 1407. The transmitter 1403 and thereceiver 1405 may be located in, for example, the top slot 693 of theinventive valve/sensor assembly 645 (FIG. 7). The receiver 1405 maydetect a light beam 1409 (transmitted by the transmitter 1403) thatreflects off of the wafer W, to indicate wafer presence (rather thandetect a light beam that passes between a light transmitter and areceiver to indicate wafer absence as with the through-beam sensor 1201of FIG. 12).

[0093] Thus, for the reflection-based sensor system 1401, the change inthe output signal of the receiver 1405 is measured when the slot 1131allows the light beam 1409 to pass therethrough as compared to when thewafer W reflects the light beam 1409 toward the receiver 1405. When thelight beam 1409 passes through the slot 1131, the output signal of thereceiver 1405 has a first signal value (interrupted state). When thewafer W reflects the light beam 1409, the output signal of the receiver1405 has a second signal value (non-interrupted state). The change inthe output signal of the receiver 1405 may be used for wafer positioningin a manner similar to that of process 1300 (FIG. 13).

[0094] Both the through-beam sensor system 1201 (FIGS. 12-13) and thereflection-based sensor system 1401 (FIG. 14) may determine whether thewafer W is present on the blade 1121. As the wafer handler 19 passesthrough the sensor system 1201, 1401, the light beam 1205, 1409 may passthrough the center hole 1129 (FIG. 11) of the blade 1121 if the wafer Wis not present on the blade 1121. Otherwise, if the wafer W is presenton the blade 1121, the wafer W blocks the light beam 1205, 1409.Detection of the leading or trailing edge of the wafer W similarly mayindicate wafer presence. The light beam 1205, 1409 may be projected atan angle relative to either the lid 41 of the transfer chamber 15 or thetop slot 693 of the inventive valve/sensor assembly 645. The angledlight beam may reduce the possibility that the receiver 1207, 1405 willdetect other sources of light.

[0095] The foregoing description discloses only exemplary embodiments ofthe invention. Modifications of the above-disclosed apparatus and methodwhich fall within the scope of the invention will be readily apparent tothose of ordinary skill in the art. As previously described, theinventive valve/sensor assembly 445, 645 may be employed with anyconventional door assembly, may include the use of a reflector asdescribed in U.S. Pat. No. 5,980,194, and may center a wafer using anyconventional wafer-positioning technique.

[0096] While the inventive valve/sensor assemblies of the presentinvention have been described primarily with reference to thefabrication tool 11 and the transfer chamber 15 (FIG. 1A), it will beunderstood that the transfer chamber 13 or any other chamber orfabrication tool may be similarly configured

[0097] Accordingly, while the present invention has been disclosed inconnection with exemplary embodiments thereof, it should be understoodthat other embodiments may fall within the spirit and scope of theinvention, as defined by the following claims.

The invention claimed is:
 1. A door assembly having: a first positionadapted to seal an opening of a chamber; a second position adapted toallow at least a blade of a substrate handler to extend through theopening of the chamber; and a mounting mechanism adapted to couple thedoor assembly to the chamber, the mounting mechanism having a viewportadapted to allow at least one transmitter and at least one receiver tocommunicate through the viewport of the mounting mechanism so as todetect a presence of a substrate.
 2. A door assembly having: a firstposition adapted to seal an opening of a chamber; a second positionadapted to allow at least a blade of a substrate handler to extendthrough the opening of the chamber; a mounting mechanism adapted tocouple the door assembly to the chamber; and at least one of a lighttransmitter and a light receiver coupled to the mounting mechanism so asto allow detection of a presence of a substrate.
 3. A mounting mechanismadapted to couple a door assembly to a chamber, the mounting mechanismhaving a viewport adapted to allow at least one transmitter and at leastone receiver to communicate through the viewport of the mountingmechanism so as to detect a presence of a substrate.
 4. A methodcomprising: providing a chamber having a valve/sensor assemblycomprising: a door assembly having: a first position adapted to seal anopening of the chamber; a second position adapted to allow at least ablade of a substrate handler to extend through the opening of thechamber; and a mounting mechanism coupled to the chamber; and a sensorsystem having a transmitter and a receiver adapted to detect a presenceof a substrate and to communicate through at least a portion of the doorassembly; transporting a substrate through the opening of the chamberwith a substrate handler; and detecting whether the substrate is on thesubstrate handler with the sensor system.
 5. The method of claim 4further comprising determining whether the substrate is centered on ablade of the substrate handler.
 6. The method of claim 5 furthercomprising adjusting placement of the substrate on a substrate pedestalif the substrate is not centered on the blade of the substrate handler.7. A method comprising: providing a chamber having a valve/sensorassembly comprising: a door assembly having: a first position adapted toseal an opening of the chamber; a second position adapted to allow atleast a blade of a substrate handler to extend through the opening ofthe chamber; and a mounting mechanism coupled to the chamber; and asensor system having a transmitter and a receiver adapted to detect apresence of a substrate and to communicate through at least a portion ofthe door assembly; transporting a substrate through the opening of thechamber with a substrate handler; determining whether the substrate iscentered on a blade of the substrate handler; and adjusting placement ofthe substrate on a substrate pedestal if the substrate is not centeredon the blade of the substrate handler.
 8. A method comprising: providinga chamber having a valve/sensor assembly comprising: a door assemblyhaving: a first position adapted to seal an opening of the chamber; asecond position adapted to allow at least a blade of a substrate handlerto extend through the opening of the chamber; and a mounting mechanismcoupled to the chamber, the mounting mechanism having a viewport; and asensor system having a transmitter and a receiver adapted to detect apresence of a substrate and to communicate through the viewport of themounting mechanism; transporting a substrate through the opening of thechamber with a substrate handler; and detecting whether the substrate ison the substrate handler with the sensor system.